January 27, 1998 Flying Real-World Weather

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by	Mike Busch

About the Author ... Mike Busch is editor-in-chief of AVweb, a member of the technical staff at Cessna Pilots Association, and in a prior lifetime was a contributing editor for The Aviation Consumer and IFR Magazine. A 6,000-hour commercial pilot and CFI with airplane, instrument and multiengine ratings, Mike has been flying for 36 years and an aircraft owner for 33. For the past 14 of those years, he's owned and flown a Cessna T310R turbocharged twin, which he maintains himself. In his never-ending quest to become a true renaissance man of aviation, Mike's on the verge of earning his A&P mechanic certificate. Mike and his wife Jan reside on the central coast of California in a semi-rural area where he can't get DSL or cable TV.

Several decades ago, my primary flight instructor taught me that being a safe pilot meant staying on the ground when the weather didn't look good. When I got my instrument rating a few years later, my CFII cautioned me against flying when icing or thunderstorms were anticipated.

Such advice may be okay for pilots who fly for recreation, but it's simply unrealistic if you fly for business and use your airplane as a serious transportation tool. This is doubly true if you fly transcontinental distances, as I do several times a year. It's seldom possible to fly 2,000 nautical miles without having to traverse at least one major weather system.

Naturally, there are times when the weather is bad enough that staying on the ground is the only prudent course. Even the airlines occasionally cancel flights due to weather. But unless we can operate with a fairly high probability of getting where we need to go when we need to be there, the airplane can't be counted on for serious business travel.

We've all heard the cliché: there are old pilots and bold pilots, but no old bold pilots. Unfortunately, it's not that simple. Weather flying requires a certain measure of boldness. The question is: how much is too much?

Equipment List

Obviously, what sort of weather we take on might be influenced by what kind of equipment we're flying. Single or twin? Turbocharged or normally-aspirated? Boots? Hot props? Stormscope? Weather radar?

But to be honest, I think equipment is overrated. For twenty years and thousands of hours, I did serious long-distance weather flying in a 1968 Cessna Skylane and later a 1972 Bellanca Super Viking — both single-engine, normally-aspirated airplanes with no deicing or weather avoidance gear or even dual vacuum pumps. The Skylane didn't even have an autopilot. For the last decade, most of my trips have been flown in my 1979 Cessna T310R — a turbocharged twin approved for flight into known icing conditions and with a Stormscope.

Yet I cannot recall a single trip flown in the 310 that would have been cancelled had I been flying the Skylane or Viking. When I think about the scariest weather flying episodes I've experienced over the past 30 years, it strikes me that they would have been scary whether I was flying a Citabria or a Citation. I won't deny that flying more sophisticated and capable equipment certainly contributes to my comfort level when tackling difficult weather, and affects some weather-avoidance tactics — such as whether to fly above the weather, below it or around it — but it doesn't influence my basic go/no-go decision very much.

Human Factors

What's more important to me are human factors considerations. Am I feeling fit and rested, or fatigued? How about my instrument flying proficiency: curent and sharp, or rusty? Do I really have the intestinal fortitude to handle a couple of hours of moderate turbulence without losing my lunch? What is my inner voice saying?

Equally important, if not more so, is whether or not I'm carrying passengers. My wife, for example, is a nervous flyer who is terrified of turbulence and has half the "bladder endurance" that I do. I've frequently cancelled or delayed flights when she was along that I'd have made without hesitation if I was flying alone. When I'm flying with passengers that I don't know quite as well as my wife, I might have to interview each one in some depth before deciding whether or not the flight can be made without traumatizing them. (When flying in challenging weather, the last thing I want to deal with is a cabin full of white knucklers.)

The Big Picture

To me, the most important part of briefing for a long flight is getting the big picture. Am I flying from good weather to bad, or bad weather to good? (I much prefer the latter.) What is the overall weather trend: deteriorating, improving, or steady-state? Would the weather would be better if I waited a few hours, or checked into a hotel and left first thing in the morning?

I find that it's hard to get the big picture from a standard FSS or DUATS pilot weather briefing. My usual source of big-picture information is The Weather Channel. I'll usually start keeping an eye on TWC for several days prior to departing on a major trip. A picture is worth 1,000 words. I've even been known to choose one hotel over another based on TWC availability when making reservations for a R.O.N. stopover.

Cable TV "superstations" are also great sources for regional weather information. For example, WGN-Chicago provides exceptional weather graphics for the Great Lakes area, and has TV meteorologists who really know the idiosyncrasies of the region's weather. Other good regional weather sources on cable TV include KDVR-Denver, KOMO-Seattle, KTLA-Los Angeles, and WWOR-New York, among others.

Over the past couple of years, I've started to rely more and more on the Internet for getting the big picture. I carry my notebook computer everywhere I go so I can access weather information on the World Wide Web, as well as obtain briefings and file flight plans using DUATS. The weather graphics on the Web are absolutely superb, and it's available on demand...no need to wait as with TV.

Here are a few of my favorite Internet weather sites. You might want to bookmark them in your web browser for future reference. There are tons more on the AVweb weather page.

Preflight Briefing

By the time I obtain my preflight weather briefing, I already have a pretty good idea of the big picture. As a general rule, I prefer to obtain my pre-flight briefing using DUATS so that I can review the raw information myself without having it "filtered" by an FSS briefer. I get particularly exasperated at briefers who try to put their own "spin" on the weather, rather than just giving it to me straight. (I just want to scream and hang up whenever I hear a briefer tell me "VFR not recommended" when I call for an IFR briefing!)

An exception to this rule occurs when I'm worried about the weather at the departure airport, because the briefer at the local FSS can sometimes offer worthwhile local weather knowledge. Telephoning the FSS is also convenient for quick updates during fuel stops when computer access is not available. But regardless of whether the briefing is by telephone or computer, it's important to keep in mind some of the limitations of the aviation weather forecasts it contains.

About Forecasts

For one thing, forecasts tend to be pessimistic. Weather forecasting is an uncertain business, and the forecasters who prepare aviation weather products have a natural tendency to make worst-case predictions. Many FSS briefers tend to inject their own dose of pessimism into their briefings. If there's one thing I've learned in three decades of weather flying, it's that the weather is almost always better than forecast, seldom worse. I can't count the number of times I've received a gloomy preflight briefing, only to discover that the actual flight was a piece of cake.

Another important limitation of aviation forecasts is that they are based on probabilities. Just because the forecast says rain or snow is likely over a large multi-state region doesn't mean that it's going to rain or snow at any particular spot in that region (such as your destination airport). In fact, it's not at all unusual to fly across such an area without ever encountering adverse weather.

There are certain weather events that are nearly impossible to forecast with any accuracy at all. Icing is foremost among these. As far as I'm concerned, standard icing AIRMETs are almost worthless. The only source of trustworthy icing information in a preflight weather briefing comes from PIREPs. One of my great frustrations is that pilots aren't more conscientious about filing PIREPs when flying in areas where icing is forecast...especially "negative icing" PIREPs (which is, after all, exactly what other pilots need to know).

The new experimental "neural net" models for forecasting icing conditions have considerable promise, however — you can check these out on the NOAA Aviation Weather Center web site.

Forecasters do a better job with thunderstorms, but they still have a tough time predicting exactly where or when the storms will develop, or whether they'll be readily circumnavigable or not.

On the California coast (where I'm based), low stratus and fog frequently develops in the evening and burns off in the morning. I find that forecasters do a pretty good job of predicting whether or not fog will form, but they're often wrong about when it will develop (sometimes by several hours one way or the other).

The bottom line is that I'm skeptical about aviation weather forecasts. In the absence of "hard" information (such as PIREPs and current surface and radar reports), I'm inclined to launch and take a look for myself...provided I'm sure that I have a "solid gold out" in case things look grim.

Finally, it's important to recognize that the accuracy of aviation weather forecasts deteriorates rapidly as they project further into the future. A terminal forecast may be fairly accurate for the next couple of hours, but the prediction for six hours out should be considered little more than an educated guess. If you're flying a 4 or 5 hour leg, it doesn't make much sense to depend on a preflight briefing for the weather at your destination, because that info will be at least 6 hours old by the time you arrive.

Inflight Updates

Consequently, it's important to keep close tabs on the weather while you're enroute. One of the best ways to do that is to monitor both Center and Flight Watch and listen to both sides of the conversations. It's especially useful to hear pilots submitting PIREPs, because you can often tell as much from their tone of voice as from the report itself. You're also likely to hear a lot of stuff that never makes it onto the weather wire, like pilots requesting altitude changes or weather deviations.

I also make a habit of keeping an eye on the clock and calling Flight Watch a few minutes after the top of each hour to get an update on the destination weather. After a few hours of these checkpoints, I have a real good feeling for the trend, and have plenty of time to anticipate problems and formulate alternatives. For example, if I'm headed for home after dark and worried if I can beat the fog, I'll keep close tabs on the hourly temperature/dewpoint spread and get a pretty good idea of when the airport is likely to go below minimums.

Flying Ice

The NTSB has ruled that forecast icing conditions are considered to be "known icing," which means in theory that most light planes are grounded whenever the forecast calls for a chance of ice. Get real! If we stayed on the ground whenever ice was forecast, we couldn't fly for 4 or 5 months out of the year in many portions of the country. And so far as I can determine, the FAA has never pursued a volation against an airman for flying a non-known-ice airplane in forecast icing conditions except when an accident occurred.

While I'm not prepared to accept the NTSB's guidance on ice flying, it is necessary to establish some basic rules. For example, I have no reservations about descending through an icing layer at my destination, especially if it's above freezing at the surface. On the other hand, a departure that requires me to climb through an icing layer gives me considerable pause. I have to be darned sure that I can get on-top without picking up much ice before tackling such a departure. This is one of the few situations where a twin has a big advantage over a single, because although twins don't cruise significantly faster than singles, they do have a lot more climb capability.

The scariest ice experience I ever had occurred in the winter of 1970 while I was heading home to California from Minneapolis in my Skylane. I wound up getting stuck in Rapid City, S.D., for several days while I waited out a big snowstorm. Finally, the snow stopped and I headed out to the airport and went to the FSS for in-person briefing. I asked about icing PIREPs, and the briefer told me about a Cessna 150 that was practicing holding patterns at 6,000' and reporting only occasional light rime ice. He also said that a United 737 was due in shortly and might be able to provide information on tops and icing.

The United flight landed as advertised, and as soon as the last passenger deplaned, I ran up the airstair, headed for the cockpit, and asked the first officer if he could give me an in-person PIREP. He replied that the tops were about 12,000 and that he hadn't noticed any icing during the descent into Rapid City.

"It's essential to take immediate action at the first sign of icing. Don't just sit there in denial... do something!"

Armed with that information, I returned to the FSS, filed an IFR flight plan westbound, and launched into the soup. Although it was below freezing on the surface that day, I experienced no icing during the climb until passing about 7,000' at which point I started picking up a little. By the time I reached 8,000' I realized my rate of climb had gone to zero and the engine was starting to lose power. The only way I could restore power was to use full carburator heat. It became clear that there was no way I was going to be able to climb on-top.

I advised Center that I was picking up moderate ice, couldn't maintain altitude, and needed to return to Rapid City. The controller gave me a clearance to return and descend. By the time I reached the outer marker, I realized that my windshield was totally iced over and completely opaque. The defroster managed to clear only a dime-sized hole right above the hot air outlet. I wound up shooting the ILS and feeling for the runway. The landing was a little "firmer" than usual, and the impact caused a large quantity of ice to fall off the airplane.

Upon taxiing in and shutting down, I discovered that there was 3/4-inch of ice on the wing leading edges and wing struts, and that the induction air filter was completely iced over. I pulled a foot-long piece of ice from the wing and plunked on the FSS counter, saying "here's my pilot report". I then checked back into the motel, at which point my knees went weak when I realized just how close I'd come to getting in serious trouble.

Could I have made this flight successfully had I been flying a known-ice-equipped Turbo 310 instead of a Skylane? Maybe, but maybe not. I'm sure I could have climbed higher than 8,000' in the T310R, but whether I could have made it to on-top is unknowable. If not, the windshield hot-plate would have come in handy when landing back at Rapid City!

I learned several things from that close call:

1. No matter how thoroughly you brief, you can never be sure about icing until you fly it.

2. Trying to climb through an icing layer in a light plane is sometimes impossible.

3. Most important, it's essential to take immediate action at the first sign of icing.

(I also learned that a Skylane can haul quite a load of ice without falling out of the sky. I hate to think of what would have happened had I been flying a Mooney!)

The same time-is-of-the-essence attitude is important when ice is encountered enroute. Don't just sit there in denial...do something! There are three possible ways to escape from an icing encounter:

1. Climb (if you think you can get on-top)

2. Descend (if you think you can get below the freezing level)

3. Make a 180 and retreat

If you can't decide whether to climb or descend, try climbing first because you can always descend later (but necessarily not vice-versa). A turbocharger often makes climbing the preferred option: if you can't climb to on-top, you still may be able to climb into cold enough temperatures that icing is no longer possible. (Icing rarely occurs below -20°C).

As soon as you've resolved your immediate icing problem, be sure to file a PIREP so that other pilots can benefit from your knowledge. It's even more important to file PIREPs when you find that there's no ice despite the forecast. If you think about it, reports of ice-free altitudes are precisely the sort of thing that other pilots need to know about.

Thunderstorms

While ice can be penetrated (in limited quantities), thunderstorms cannot. Whether we're flying a Skyhawk or Citation or Boeing, we have to steer clear of convective cells. To do this, we must depend on our weather-avoidance equipment: weather radar, sferics detector (Stormscope or Strikefinder), or Mark I Eyeball.

I've flown with both radar and sferics. I prefer sferics for enroute weather avoidance (because it sees further and detects turbulence better), and radar for close-in avoidance during the departure or arrival phase (because it provides accurate distance information). Having both radar and sferics is even better.

I have a strong preference for avoidance-by-eyeball and use it whenever possible. A good look at a towering cumulus cloud can tell you a lot more about what's going on than any electronic box. If you're flying a turbo, climbing up to the low Flight Levels can really help. Although you usually can't climb above the CB tops, it's often possible to get a good look at them at FL200 and hopefully circumnavigate them. But eyeball avoidance has some serious limitations: it's useless with embedded thunderstorms, and it doesn't work very well after dark.

If your airplane is equipped with radar, do yourself a favor and take a good radar course. Weather radar requires considerable interpretation, and most pilots don't have the training required to use it effectively. Both Dave Gwinn and Archie Trammel offer excellent weather radar courses at numerous locations around the country. Archie Trammel's course is also available on videotape.

In the absence of airborne weather radar, it's tempting to ask ATC for vectors around weather. But in my experience, this is risky business because many ATC radar sites aren't very good a painting weather, and most controllers have little or no training in interpreting weather returns. I remember flying into Boston Logan in my Skylane many years ago. New England was awash with convective activity, and the Boston Center controller was doing his level best to vector me around the worst of the weather. But despite the controller's good intentions, he wound up vectoring me right through the middle of a couple of cells. Frankly, it scared the hell out of me.

My 310 is equipped with an old WX-10 Stormscope, and over the years I've learned to trust it. I've never blundered into serious turbulence when following the Stormscope. When given the choice of an airborne Stormscope or ATC radar, I'll take the Stormscope every time.

I recall a trip several years ago when I was flying from New Hampshire to Pennsylvania. A line of thunderstorms cut across upstate New York. The Stormscope was lit up like a Christmas tree, but there seemed to be a decent-sized gap in the dots. I advised Albany Approach that I needed to make a turn to penetrate the weather where the Stormscope showed a "soft spot". The controller told me that according to his radar, my requested heading would take me straight into the worst part of the weather.

I decided to trust the Stormscope, despite the controller's increasingly panicky admonitions. I soon entered the clouds. Then it started to rain, and the rain got progressively heavier. Yet the Stormscope continued to indicate that there were no dots stright ahead. The controller called me every couple of minutes to make sure I was okay; he was clearly frightened that I would get in trouble and he'd have a lot of extra paperwork to do. After about 15 minutes of this, the rain stopped and I flew into the clear. I advised the controller that I'd encountered heavy rain but absolutely no turbulence. He was clearly surprised (and relieved).

This episode serves to underscore the difference between radar and sferics. Radar detects water, while sferics detects electrical discharges. Electrical discharges invariably mean that there are strong updrafts and downdrafts, but water doesn't necessarily mean turbulence. Ground-based weather radar is designed to measure cloud tops, and airborne weather radar can do the same thing if the pilot knows his stuff (and is handy with the tilt control). But ATC radar offers no information on tops, so the controller can tell you about rain but not necessarily turbulence.

Using a Stormscope effectively requires interpretation, although not as much as airborne weather radar does. I've found that one of the keys to Stormscope use is the frequent use of the "clear" button. Although clusters of dots on the screen usually depict convective activity, the best way to assess storm intensity is to clear the display and see how fast the dots reappear. The faster the dots appear, the stronger the storm.

Another important lesson is that sferics equipment provides quite accurate direction information but only a vague idea of distance. A cluster of dots on the Stormscope display at the 50-mile range ring might not mean the cell is 50 miles away. If it's a weak storm, it might be a closer than that; if it's unusually strong, it might be a good deal further way. Often, a single cell will produce electrical discharges of various intensities that result in dots on the screen at various ranges; this is known as "radial spread." Although the latest Series II Stormscopes employ software tricks to reduce radial spread, it exists in some measure with all sferics devices.

Summary

The only rule about weather flying is that there are no hard-and-fast rules. That's why judgment and experience are required. Here's a quick review of some strategies I use:

• I consider the human factors affecting me and my passengers before making a go/no-go decision. Even if my aircraft can handle the weather, maybe its occupants can't.
   

• Before any long trip, I get the big picture by keeping an eye on The Weather Channel or some of the better Internet sites for a few days before I depart.
   

• I get the best preflight briefing possible, of course, but I temper it with the knowledge that aviation forecasts often paint a picture worse than what I'll actually encounter, but also that some weather hazards like icing cannot be forecast with any real accuracy.
   

• While enroute, I stay tuned in to all available sources of in-flight weather information, including real-time PIREPs and hourly updates from Flight Watch.
   

• I seldom let an icing forecast discourage me from flying (icing PIREPs are another matter!), but I take immediate steps to get out of ice when I encounter it, then file a PIREP for the next guy.
   

• When faced with thunderstorms, I use all available methods to circumnavigate them: weather radar, sferics gear, and especially my eyes. But I've learned to be skeptical of weather-avoidance vectors from ATC.

Most important, after obtaining all available weather information, I listen closely to "that little voice" that tells me whether or not it's okay to go. Call it "gut feeling" or "the voice of experience" if you prefer. Whatever you call it, so far it hasn't let me down.